First, the Sargeant went there because of a suspicious person/burglary in progress. When Gates came to the door, the prudent thing to do is to get him out of the house to talk. Why? Because he could be in danger, as in a perp inside the house, holding a gun to him or a loved one. Or, the perp could be hiding in the house, unbeknownest to Gates.
When Gates acted like an azz and said he was gong back int eh house to get his ID, the officer followed him in. Why? Because if Gates was a nut job (which he was acting like) he could have returned with a gun.
All Gates had to do was to say, Thank you for coming, but it was me trying to get in my back door. There is no emergency, here is my ID. Sorry to have caused a false alarm.
But, instead he said "You're a racist", "you're just doing this because I am black", "this is what it is like to be a black man", "I'll talk to yo' mamma", "do you know who I am?" and who knows what other stupid things, all the while trying to get in touch with the police chief.
The guy is a professor. One would think he has better manners and social skills than he showed. But, he showed his azz, acting like a low rent



.
Just because the charges were dropped doesn't mean Gates didn't do what he was arrested for. It just means that the DA wasn't going to prosecute the professor for a misdemeanor. He was given special treatment because of his status.
Anyone else would have had to answer the charges.
Personally, it has been my experience that Blacks are more prejudiced against Whites than the other way around. I have been the victim of racially motivated hate, physically attacked because I am White. My friend was shot and crippled for life by a Black man because she is White. We were both called racial slurs during the attacks.
I am sick of people pretending only Whites are capable of racism. Wake up. Gates made an azz of himself because of his preconceived notions of White police officers. That is called racism.
As a White person, I am tired of White people being blamed for the problems in the Black community and am insulted to be pre-judged as a racist because I am White.
I think the Black community would be surprised to know that MOST White people don't think about "race" when dealing with people. We deal with the person, not the race, and Black people are being mislead by others who have an agenda to keep people in a state of racial tension.